Jacklyn M. Gallagher: “Towards the discovery of small molecules that restore the expression and function of CTD variants”

ABSTRACT

Over 100 loss-of-function (LOF) mutations within the SLC6A8 creatine transporter (CT1) are known to cause creatine transporter deficiency (CTD) syndrome. Most of these mutations enhance CT1 misfolding and degradation, and the resulting loss of the transporter protein ultimately compromises creatine uptake within the brain and other organs. Creatine uptake could therefore be restored by small molecule “correctors” that rescue the expression of misfolded variants, the development of which has recently revolutionized the treatment of several other genetic diseases of membrane protein misfolding. Cumulative observations concerning the mechanistic effects of drugs targeting related SLC6 transporters such as the serotonin (SERT) and dopamine (DAT) transporters suggest compounds that selectively bind to their inward-facing (IF) conformation generally enhance their expression and maturation. Based on these considerations, we set out to identify small molecules that selectively bind to the IF conformation of CT1 in order to restore the expression and activity of misfolded CT1 variants. Towards this goal, we developed a virtual screening approach to identify small molecules that selectively bind to the IF conformation of CT1, then profiled their effects on CT1 expression. Of our top 53 candidates, we identify several that alter the expression profile of WT CT1 and a few that enhance its expression at the plasma membrane. We are currently working to determine how these molecules impact CT1 function and how they impact pathogenic CT1 variants. Additionally, based on the structures of our top hits, we are currently searching for second-generation compounds with increased potency. These results represent an important step toward the development of novel pharmacological chaperones for the treatment of CTD.